Interleukin-2 as a neuromodulator possibly implicated in the physiopathology of sudden infant death syndrome

Neurochemical Alterations in Sudden Unexplained Perinatal Deaths-A Review

Sudden unexpected perinatal collapse is a major trauma for the parents of victims. Sudden infant death syndrome (SIDS) is unexpected and mysterious death of an apparently healthy neonate from birth till 1 year of age without any known causes, even after thorough postmortem investigations. However, the incidence of sudden intrauterine unexplained death syndrome (SIUDS) is seven times higher as compared with SIDS. This observation is approximated 40-80%. Stillbirth is defined as death of a fetus after 20th week of gestation or just before delivery at full term without a known reason. Pakistan has the highest burden of stillbirth in the world. This basis of SIDS, SIUDS, and stillbirths eludes specialists. The purpose of this study is to investigate factors behind failure in control of these unexplained deaths and how research may go ahead with improved prospects. Animal models and physiological data demonstrate that sleep, arousal, and cardiorespiratory malfunctioning are abnormal mechanisms in SIUDS risk factors or in newborn children who subsequently die from SIDS. This review focuses on insights in neuropathology and mechanisms of SIDS and SIUDS in terms of different receptors involved in this major perinatal demise. Several studies conducted in the past decade have confirmed neuropathological and neurochemical anomalies related to serotonin transporter, substance P, acetylcholine α7 nicotine receptors, etc., in sudden unexplained fetal and infant deaths. There is need to focus more on research in this area to unveil the major curtain to neuroprotection by underlying mechanisms leading to such deaths.

A systematically structured review of biomarkers of dying in cancer patients in the last months of life; An exploration of the biology of dying

BACKGROUND

The Neuberger review made a number of recommendations to improve end of life care, including research into the biology of dying. An important aspect of the biology of dying is the identification of biomarkers as indices of disease processes. Biomarkers have the potential to inform the current, limited understanding of the dying process and assist clinicians in recognising dying, in particular how to distinguish dying from reversible acute deterioration.

OBJECTIVES

To critically appraise the literature on biological factors that may be used as prognostic indicators in advanced cancer patients and to identify candidate biomarkers of the dying process that can be measured serially in cancer patients' bodily fluids.

METHODS

A systematically structured review was conducted using three electronic databases. A hand search of six peer-reviewed journals and conference abstracts was also conducted. Studies reporting prognostic biomarkers in cancer patients with a median survival of ≤90 days and post-mortem studies were included. Final levels of evidence and recommendations were made using the Evidence Based Medicine modified GRADE system.

RESULTS

30 articles were included. Seven prognostic biological factors demonstrated Grade A evidence (lymphocyte count, white blood cell count, serum C-reactive protein, albumin, sodium, urea and alkaline phosphatase). An additional eleven prognostic factors were identified with Grade B evidence (platelet count, international normalised ratio, serum vitamin B12, prealbumin, bilirubin, cholesterol, aspartate aminotransferase, alanine transaminase, lactate dehydrogenase, pseudocholinesterase and urate). A number of biomarkers were specifically identified in the last two weeks of life but limitations exist. No post-mortem studies met the inclusion criteria.

CONCLUSION

The biology of dying is an important area for future research, with the evidence focused on signs, symptoms and prognostic factors. This review identifies a number of common themes shared amongst advanced cancer patients and highlights candidate biomarkers which may be indicative of a common biological process to dying.

Collecting biological material from palliative care patients in the last weeks of life: a feasibility study

OBJECTIVE

To assess the feasibility of prospectively collecting biological samples (urine) from palliative care patients in the last weeks of life.

SETTING

A 30-bedded specialist hospice in the North West of England.

PARTICIPANTS

Participants were adults with a diagnosis of advanced disease and able to provide written informed consent.

METHOD

Potential participants were identified by a senior clinician over a 12-week period in 2014. They were then approached by a researcher and invited to participate according to a developed recruitment protocol.

OUTCOMES

Feasibility targets included a recruitment rate of 50%, with successful collection of samples from 80% who consented.

RESULTS

A total of 58 patients were approached and 33 consented (57% recruitment rate). Twenty-five patients (43%) were unable to participate or declined; 10 (17%) became unwell, too fatigued, lost capacity, died or were discharged home; and 15 (26%) refused, usually these patients had distressing pain, low mood or profound fatigue. From the 33 recruited, 20 participants provided 128 separate urine samples, 12 participants did not meet the inclusion criteria at the time of consent and 1 participant was unable to provide a sample. The criterion for a urinary catheter was removed for the latter 6 weeks. The collection rate during the first 6 weeks was 29% and 93% for the latter 6 weeks. Seven people died while the study was ongoing, and another 4 participants died in the following 4 weeks.

CONCLUSIONS

It is possible to recruit and collect multiple biological samples over time from palliative care patients in the last weeks and days of life even if they have lost capacity. Research into the biological changes at the end of life could develop a greater understanding of the biology of the dying process. This may lead to improved prognostication and care of patients towards the end of life.

Neurochemical abnormalities in the brainstem of the Sudden Infant Death Syndrome (SIDS)

The brainstem has been a focus in Sudden Infant Death Syndrome (SIDS) research for 30 years. Physiological and animal model data show that cardiorespiratory, sleep, and arousal mechanisms are abnormal after exposure to SIDS risk factors or in infants who subsequently die from SIDS. As the brainstem houses the regulatory centres for these functions, it is the most likely site to find abnormalities. True to this hypothesis, data derived over the last 30 years shows that the brainstem of infants who died from SIDS exhibits abnormalities in a number of major neurotransmitter and receptor systems including: catecholamines, neuropeptides, acetylcholinergic, indole amines (predominantly serotonin and its receptors), amino acids (predominantly glutamate), brain derived neurotrophic growth factor (BDNF), and some cytokines. A pattern is emerging of particular brainstem nuclei being consistently affected including the dorsal motor nucleus of the vagus (DMNV), nucleus of the solitary tract (NTS), arcuate nucleus (AN) and raphe. We discuss the implications of these findings and directions that this may lead in future research.

Intact numbers of cerebellar purkinje and granule cells in sudden infant death syndrome: a stereologic analysis and critical review of neuropathologic evidence

Despite much research during recent decades, the etiology and pathogenesis of sudden infant death syndrome (SIDS) remain unknown. Because of the role of the cerebellum in respiratory and cardiovascular control, it has been proposed that it plays an important role in the pathogenesis of SIDS. To date, 5 postmortem studies on the cerebellum of SIDS cases have yielded conflicting results. Using a rigorous design-based stereologic approach, we investigated postmortem cerebella from 9 SIDS patients who died between 2 and 10 months of age and from 9 age- and sex-matched control children. Neither the volumes of the cerebellar external granule cell layer, molecular layer, internal granule cell layer (including the Purkinje cell layer), and white matter nor the total numbers of Purkinje cells, granule cells in the internal granule cell layer, and the number of granule cells per Purkinje cell showed statistically significant differences between the SIDS cases and the controls. Based on these observations, we conclude that structural alterations in cerebellar development are not involved in the etiology and pathogenesis of SIDS.

Effects of simulated reflux laryngitis on laryngeal chemoreflexes in newborn lambs

It has been suggested that reflux laryngitis (RL) is involved in apneas-bradycardias of the newborn. The aim of the present study was to develop a unique RL model in newborn lambs to test the hypothesis that RL enhances the cardiorespiratory components of the laryngeal chemoreflexes (LCR) in the neonatal period. Gastric juice surrogate (2 ml of normal saline solution with HCl pH 2 + pepsin 300 U/ml) (RL group, n = 6) or normal saline (control group, n = 6) was repeatedly injected onto the posterior aspect of the larynx, 3 times a day for 6 consecutive days, via a retrograde catheter introduced into the cervical esophagus. Lambs instilled with gastric juice surrogate presented clinical signs of RL, as well as moderate laryngitis on histological observation. Laryngeal chemoreflexes were thereafter induced during sleep by injection of 0.5 ml of HCl (pH 2), ewe's milk, distilled water or saline into the laryngeal vestibule via a chronic, transcutaneous supraglottal catheter. Overall, RL led to a significantly greater respiratory inhibition compared with the control group during LCR, including longer apnea duration ( P = 0.01), lower minimal respiratory rate ( P = 0.002), and a more prominent decrease in arterial hemoglobin saturation (SpO2) ( P = 0.03). No effects were observed on cardiac variables. In conclusion, 1) our unique neonatal ovine model presents clinical and histological characteristics of RL; and 2) the presence of RL in newborn lambs increases the respiratory inhibition observed with LCR, at times leading to severe apneas and desaturations.

A perspective on SIDS pathogenesis. the hypotheses: plausibility and evidence

Several theories of the underlying mechanisms of Sudden Infant Death Syndrome (SIDS) have been proposed. These theories have born relatively narrow beach-head research programs attracting generous research funding sustained for many years at expense to the public purse. This perspective endeavors to critically examine the evidence and bases of these theories and determine their plausibility; and questions whether or not a safe and reasoned hypothesis lies at their foundation. The Opinion sets specific criteria by asking the following questions: 1. Does the hypothesis take into account the key pathological findings in SIDS? 2. Is the hypothesis congruent with the key epidemiological risk factors? 3. Does it link 1 and 2? Falling short of any one of these answers, by inference, would imply insufficient grounds for a sustainable hypothesis. Some of the hypotheses overlap, for instance, notional respiratory failure may encompass apnea, prone sleep position, and asphyxia which may be seen to be linked to co-sleeping. For the purposes of this paper, each element will be assessed on the above criteria.